Recovery of ion exchange regenerant



R. H. COTTON ET AL RECOVERY 0F ION EXCHANGE REGENERANT May 1l, 1954 2 Sheets-Sheer. l

Filed Feb. 20, 1950 x. IIJ I1 a ATTOR N EYS Patented May 11, 1954 UNITED STATES PATENT OFFICE Application lieb'ruari7 20, 1950, Serial No. 145,208

(Cl. 12V- 46) Claims.

This invention relates to the regeneration pf ion exchange material, and more particularlyto the regeneration of anion exchange material utilized in a process such as the purification of sugar beet juice. I

-In the conventional beet sugar factory, in ac-` cordance with methods in use for a number ofi years, the beets are cleaned, as by washing and trash separation, then cut into relativelyl long; thin slices, as by sets of rotating knives. These slices are commonly known as cassettesl and the present preferred cross section is a modified or broad V. The cossettes may be placed in cells in a diiiusion battery, which also may be continuous, and heated water passed through the same to dissolve out the sugar. Of course, the heated water also tends to Adissolve other coinpounds or constituents contained in the beets, which appear in the beet juice as impuritiesanjd which not only may produce an undesirable color or taste of the sugar, but also may interfere with subsequent boiling and crystallization operations. To remove as much of these impurities as possible, it has been customary to treat the raw juice by defecation, i. e. with lime and then with carbon dioxide, followed by filtration, with further treatment by sulphur dioxide, filtration, and passage through bone-char, kieselguhr, or the like. After such purification, the juice is evaporated, normally in several stages, until suiiiciently thick for crystallization of sugar,` the latter being accomplished in comparatively large vacuum pans. After crystallization, the ,liquid remaining in the sugar may be removed by ceri# trifuging, accompanied by Washing, the wash water being also removed, as' far as possible. Then the sugar is dried, and packaged or stored. Somewhat the same process is utilized in refining cane sugar, except that the cane' is usually crushed to expel the juice, crushing sometimes' being followed by water extraction of as much remaining sugar as possible. v i

There are, of course, certain refinements" in this general process, such as regenerative stepsin the crystallization of sugar of different degrees of purity, and utilization of the Steffens proc'-V ess. In the latter, the lime, used as dry pow'- dered lime or CaO, is first reacted with impure molasses or syrup driven out from relatively itinpure sugar, termed low green, the result of the iime reaction in the Steffens House being a calcium saccharate which is filtered from the. impurities in the molasses. This calciuml sac-y charate is added to the raw juice at first carbonation, so as to return the saccharate content tol the principal purification process. Also, the molasses may be treated 'by a barium process, to extract additional sugar content.

Recently, there lhas been considerable interest inl af' different type of purification, involving ion exchange; Thus, a cation'- exchan'ger. such as a" sulfonat'ed coal product, maybe utilizedto convert sodium, potassium, calcium or magnesium salts, certainvorganic compounds, and the like, into a corresponding acid. In other Words, the cationV exchange material exchanges H+ for Na+, K+, Ca++, Mg-tif, and the like, the acid thus formed being retained in thejuice, and the exchanged ion rem'ainingwith the cation ex'- chang'e material'. The anion exchange material has an opposite chemical property, i. e. it will tend ,to take up or absorb Athe acid, exchanging an O'I-I- ion therefor. When the anion exchange material exchanges OH for the acid radical, such as C1150?, and various organic radicals. such impurity will haveA been removed from the juice, since the H+ ofA the acid combines with the' Oifrom the anion exchange material to form H2O, and the acid` radical remains with the anion exchange material. Cation exchange materials which maybe used include certain sulfonated coals or a `sulfonated Aphenol such as C-200 (American Cyanamid Col, while anion exchange materials which may be used include certain Quaternary hydroxyl amines, or resins such as Anexj .fDeocidite or A-293-M (American Cyanamid 0o.); l

The anion andl cation exchange material, which are usually used in 'granular form, even tually become exhausted, and therefore lose effectiveness as an exchange material. At this point, it is necessary to regenerate the ion exchangev material; In' thev case of the cation exchange material, a solution of a relatively strong acid, such as I-IzSO, may be utilized forregeneration, wherein the H+ of the acid displaces Na+, K+, Ca++, Mg++, or organic anion, the resulting Na2SO4, MgSOi, and the like, being flushed from the' exchange material. The anion exchange material' may be regenerated by a basic solution, such as a solution of NazCOa, and in the case of certain of the newer synthetic resins, with NaOH or NlL-IfiOI-I.`

The ion exchange process may be used alone for purification of sugar juice, although in pres-k ent factories having defecation equipment installed, it may be morey desirable to combine ion exchange with lime defecation. In general, acid to regenerate the cation exchanger, is less costly than the caustic tor regenerate the anion exchanger. However, since the solution for regeneration of the anion exchange material car-- ries all the impurities removed by ion exchange, reuse of the basic sblution is generally impractical. Also, the solution has become more dilute 'by removal of the alkaliduring exchange, and

also by dilution with wash water and the like.

Among the objects of the present invention are to provide' a novel ionV exchange process; to pron vide such a" process which more pa'rticularlylin# wolves the regeneration of an anion exchange material; to provide such a process by which the total amount of fresh regenerant for the anion exchange material may be reduced; to provide such a process which involves a minimum of additional steps; to provide such a process which requires a comparative minimum of additional equipment; to provide such a process which can utilize products already in supply at a sugar factory or the like; and to provide such a process which may be carried out at a comparative minimum of expense and difliculty.

The above .and additional objects of this invention, together with the novel features thereof, will become apparent from the following description, taken in connection with the accompanying drawings, in which:

Fig. l is a flow sheet or diagram of a portion of a sugar factory operation, wherein ion exchange is combined with defecation;

Fig. 2 is a ow sheet or diagram of a portion of the operation illustrated in Fig. l, in which regeneration of the anion exchange material is carried out in accordance with the present invention;

Fig. 3 is a chart illustrating one example of iiow control at the anion column, when utilizing the regeneration process of this invention; and

Fig. li is a chart in which the total recoverable ammonia is plotted against the total spent regenerant evaporated, and illustrates one of the unexpected results of the process of this invention.

As illustrated in Fig. l, the raw juice, obtained either by crushing sugar cane or by extracting sugar with heated water from sugar beet slices or cossettes, may be passed to a heater, and thence to the stage known as first carbonation, at which lime, in the form of Ca(OH)2, is added, along with CO2. The milk of lime, or Ca(OH) 2, as well as CO2 gas, are conveniently produced in a lime kiln, the feed to which consists of coke and limestone, while the burned lime from the kiln is sent through a lime slacker, to produce the milk of lime. rThe lime tends to combine with impurities such as certain organic acids, converting the saine to insoluble calcium salts, while the addition of CO2 causes excess lime to precipitate as calcium carbonate. The change in hydrogen ion concentration, through the addition of lime, tends to cause some colloidal impurities to precipitate. Also, the various precipitates formed may tend to absorb still other impurities, and to trap iinely divided suspended matter. The juice containing the various precipitates and adsorbed impurities is passed to the next step, that of settling and filtration, from which the removed lime cake, containing also other precipitated or adsorbed impurities, is discarded to a settling pond or the like. From rst iiltration, the partly clarified juice is sent to second carbonation, where additional CO2 is passed therethrough, followed by a second filtration step and addition of SO2 at the thin juice tower, SO2 reducing the pH of the juice to about a neutral value. At this time, about the maximum of impurities that can be removed by lime defecation have now been removed and discarded at the lters. Thus, ion exchange can be utilized to remove additional impurities, or lime defecation can be utilized to remove a relatively smaller amount of impurities, dependence being placed upon ion exchange to remove additional impurities. Of course, as indicated previously, ion exchange alone can be relied on to purify the sugar juice.

As indicated previously, in the cation ex'- changer, l-I-lions are exchanged for Na+, K+, MgI--,L, Ca{-|, various organic radicals, and the like, an acid thus being formed in the juice and the positive ions removed from the juice remaining in the bed, normally in combined form. When the juice containing the acid reaches the anion exchanger, the OH- ion of the exchanger replaces the .acid radical, thereby removing the iinpurity and leaving in its place HCH or water. in the diagram of Fig. l, only one cation ex changer and one anion exchanger are shown, but it will be understood that there are preferably a series of exchangers, such as four of each, so that the sugar juice may be passed through three pairs in series while the other pair is being regenerated. Prior to regeneration, the sugar juice remaining in the exchanger may be displaced by water, in a step known as sweetening off, and then a reverse flow water rinse or back wash may be utilized to wash out mechanically held impurities and classify the granular material to reduce ow resmtance on subsequent passage of juice therethrough. Sulphuric acid or HzSOi, used in dilute solution, is a suitable agent for regenerating the cation exchanger beds, being passed through the bed, .and the resulting product, which will contain the positive ions removed from the sugar juice by the cation exchanger, may be collected in a spent cation regenerant tank. Similarly, a basic solution, such as ammonia, again relatively dilute, may be passed through the anion exchange material, to regenerate the OH ions therein, and cause the removal of the collected acid radicals, the result of impurities removed from the juice. rlhe ammonia may be passed through the anion exchanger bed, and then to a spent anion regenerant tank, although at certain times during regeneration, the amount of impurities is suficiently small that the ammonia can be returned to a makeup tank to which it is necessary to add fresh ammonia from time to time. Although the acid for regeneration of the cation exchange material, as well as the alkali for regeneration of the anion exchange material, is generally in cornparatively dilute aqueous solution, the solutions are usually sufficiently strong so that damage may result to sewer pipes and the like, so that it is desirable to discard the spent regenerating solutions together, so that the alkali will tend to neutralize the acid.

From the anion exchanger, the sugar juice, now relatively free of impurities, may be passed to ,the evaporators, crystallizing pans, centriiugals,

driers, and other subsequent steps in the sugar refining process.

ln accordance with the present invention, and as illustrated in Fig. 2, the ammonia solution utilized in regeneration of the anion exchange material is itself regenerated to recover as high as 98% of the ammonia and in sufficiently strong solution that no additional treatment is necessary. In Fig. 2, the piping, control valves and `other equipment for passing the juice through the anion exchange material are not shown, it being understood that the same are similar to those shown in Fig. 1.

Due to the relatively large amounts of ammo- 1 nia necessary to be passed through the anion exchange material, in regenerating the saine, the cost of such ammonia is a not inconsiderable item, and often represents a considerable portion of the cost of materials for the ion exchange process. As indicated previously, during certain portions of the regenerating cycle, the ammonia, after passage through the anion exchange material, will contain a suiiiciently small amount of impurities that it can be returned to the ammonia makeup tank. l'n addition, rinse water is preferably employed' to displace the ammonia from` the anion exchange material, so as to leave the latter as fresh as possible. Thus, in addition to an ammonia makeup tank i0 vand a line H leading therefrom controlled by a valve l2, from which the relatively dilute ammonia solution, such as between 2% and 5%, may be admitted to the anion exchanger, there may also he provided a rinse Water line I3 controlled by a valve I4, and connected with a suitable source oi rinse water, preferably either supplied from a rinse tank, as described later, or from rinsing of the cation exchanger. Fresh ammonia may be supplied to makeup tank la'i through a supply line I5, controlled bya valve i6. The discharge line l1 from the anion exchanger is provided with a valve I3 to control discharge to a sewer or the like, and also a branch i5, controlled by a valve and leading to the ammonia makeup tank It.

In order to carry out the present invention, the discharge line Ii from the anion exchanger is also provided with a branch line 2i, controlled by a valve 22 and leading to a spent regenerant tank 23. From the tank 25, the spent regenerant is passed through a line 2d to a condenser 25, which also acts as a heat exchanger, to heat the regenerant discharged from. the condenser through line 25 to an evaporator' 2l, which may be heated by steam coils or the like, or by direct introduction of steam. In the evaporator 2l, in

.accordance-with this invention, a relatively slight amount of lime, such as between 1% and 1.5%, and not over 2%, is added to the spent regenerant, and the latter is heated so as to drive oli only a fraction of the liquid, such as between 10 and 15%, and not over 22.5%. The evaporated liquid passes through vapor line 23 to condenser 25, and is condensed by heat exchange with the incoming spent regenerant, the condensate passing through a return line 29 to the ammonia makeup tank it. 1t been found, entirely unexpectedly, that the addition of approximately 1% to 1.5% lime not only tends to increase the ammonia recovery during evaporation, but also prevents the formation oiA a scale in the ammonia condenser, which is difficult to remove and tends to clog the condenser in a relatively short time. This scale has been tentatively identified as (NH01-H103, although not positively.

These unexpected results will be evident from Fig. 4, which is a chart showing curves plotted from results oi evaporating various percentages of spent regenerant when 1% and 1.5% ci lime, by weight based on the weight of the spent regenerant, were added, the percent or" total animonia recoverable being plotted against the percent of spent regenerant evaporated. shown, when 1% of lime was added, ai'ter only ,15% of the total spent regenerant was evaporated, 80% of the total recoverable ammonia was contained in the condensate, while when 1.5% lime was added and 15% of the total spent regenerant had been evaporated, between 97% and 98% oi the total recoverable ammonia was contained in the condensate, and when 22.5% ci the total spent regenerant was evaporated, approximately 100% of the recoverable ammonia was contained in the condensate. Also, when 1.5% oi lime was added and only 10% of the spent regenerant evaporated, about 90% of the recoverable ammonia was contained in the condensate. in cornparison therewith, when no lime was added, only of the ammonia was recovered by evaporating and condensing 20% of the spent regenerant, while with 10% and 15% evaporation, the recovery vwasronly 24.5% and 31.5% of the ammonia, respectively. Since the concentration of the spent regenerant tended to vary between 0.15% and1.7%, whereas 2% to 5% ammonia conce tration was desired for regeneration purposes, it is evident that this partial distillation, accompanied vby the addition of lime, is unexpectedly more economical than would be evaporation of all the distillable liquid of the spent regenerant. in addition, when 10% of the spent regenerant was evaporated, the resulting condensate contained between 2% and 5% ammonia, and when 15% ofthe spent regenerant was evaporated, the resulting condensate contained as high as 15% ammonia. rhis is a considerable advantage, since if the ammonia concentration is 'higher than that desired for regeneration purposes, dilution is very readily accomplished. However, ii the concentration were lower than that desired, then additional distillation, or concentration, would be necessary, which are thus avoided by the method kof this invention.

As a practical matter, the amount of spent regenerant evaporated is preferably about 15%, but may be only 10%, in view of the fact that the recovery of ammonia is relatively high and that between 10% and 20%, the proportional increase is relatively lower, as will be observed from the fact that the curves of Fig. 4 tend to flatten out to the right. it is ci interest to note that, although not plotted on 4, when 3% lime was added to the spent regenerant, an evaporating curve almost the same as the 1.5% lime curve was produced. This indicates that approximately i.5% lime was a critical percentage, i. e. additional lime did not tend to produce any greater recovery. The above critical value applies, of course, to the particular spent regenerant treated in ascertaining the points determining the curves of Fig. 4, and other spent regenerants, involving different amounts and/or typesoi impurities, or other factors, tended to have slightly different critical ranges of lime addition. However, none of a large number tested had a critical range of lime addition over 2%, so that approximately 2% is deemed to be the critical point of lime addition, rather than 1.5%. It is also of interest to note that, by the method of this invention, the amount oi ammonia necessary for replacement purposes has, in one plant operation, calculated to be reduced by Although the exact time of discharge to the spent regenerant tank, to the ammonia makeup tank, to the sewer, and to the rinse tank, can be vared from that shown, Fig. 3 illustrates one cycle which has been used and is indicative of the possibilities. In Fig. 3, two curves, the upper showing total solids and the lower ammoniacal nitrogen, representative of ammonia, are plotted against time. The data for these curves was taken during regeneration period of approximately 34 minutes. During the period A, i. e. for about l1 minutes, the ammonia solution or anion regenerant was passed from makeup tank I0 through line l l to the anion exchanger, and the discharge from the exchanger was sent to the spent regenerant tank 23 through line 2|, by opening valve 22. As shown, after the iirst surge of solids and ammonia, the two curves leveled off, with relatively little ammonia present in the discharge, indicative of regeneration oi the anion exchange material. However, after several minutes, such as at about the eighth minute, the total solids and also the ammoniacal nitrogen began to increase, indicative of the completion oi regeneration. Thus, during the periodB, of about 4 minutes, rinse water from line i3 was then passed through the exchanger by opening valve lll, after the ammonia from tank I had been shut o by closing valve I2. This rinse water pushed ammonia solution from the anion eX- change material, and both the total solids and the ammoniacal nitrogen increased for several mimutes. As soon as the total solids began to decrease sharply, the rinse water discharge, during period C of nve minutes, was passed directly to the ammonia makeup tank through line i9, by closing valve 22 and opening valve i9. During period 0, the total solids further decreased relatively sharply and the amount of ammonia. became considerably smaller, so that during period D of three minutes, the rinse water discharge was passed directly to the sewer by closing valve 2@ and opening valve E8, since the amount of ammonia in the rinse water discharge had decreased to the point of uneconomical recovery, and also the percentage of total solids had again become relatively large. Afterward, during period E, comprising the remainder of the total time period, when the percentage of total solids had further decreased and the amount of ammonia was relatively low, the rinse water was passed instead to a rinse tank, for reuse. Such reuse may be the rinsing of the next anion exchanger to be regenerated, as during the periods B, C,

and 13. However, the rinse discharge during the latter stage tends to be demineralized, and thus may be used for other purposes in the plant, such as mixing with chemicals, as boiler feed water, and the like. The rinse water for the anion exchanger may conveniently be obtained, during period "E, from rinse water which has first been passed through the cation exchanger, since certain compounds in raw water, such as magnesium, which tends to be removed during rinsing of the cation exchanger, may tend to remain in the anion exchange material, thus reducing its capacity.

The sequence of operation described above can,

oi course, be varied considerably, both as to time periods and as to specic place of ow. For instance, the rst discharge during regeneration, such as until the ammonia concentration reaches 'about 0.15%, may be sent directly to the sewer. Then, before or about the time that the rinse water is introduced, the discharge may be sent to the spent ammonia tank; and afterward, when the amount of ammonia in comparison with iinpurities has increased considerably, the discharge may be sent to the ammonia makeup tank. Durving this time, even though the concentration of ammonia in the discharge may he around 1 the discharge sent to the ammonia makeup tank iii may tend to dilute the 5% to 15% solution recovered by evaporation or" only to 15% of the liquid from the spent regenerant tank, lbut it can be used primarily to provide a suicient volume of liquid in the makeup tank lil, the concentration of ammonia desired being obtained through ammonia supply line 55. Finally, the remainder of the discharge may be passed to the sewer and then to the spent regenerant tank, or to the spent re- E-generant tank and then to the rinse tank, or all oi the remainder may be passed to the spent regenerant tank. Y

as will be evident from the foregoing, the method of this invention fulfills to a marked degree the requirements and objects hereinbefore set forth. The various steps of the process of this invention are integrated with the regeneration of anion exchange material, and serve not only to reduce the cost of makeup ammonia, but also to produce makeup ammonia from the spent anion regenerant which is immediately usable as makeup Without additional distillation, separation, compression, or other steps. By evaporating only a fraction of the spent regenerant, i. e. as iroin 10% to l5%, and not over 22.5%, the tendency i'or any adsorbed or otherwise trapped impurities to pass off with the ammonia, tends to be avoided. Furthermore, the sludge which has resulted from evaporation of the spent regenerant, subsequent to liming, can be passed to the sewer with the knowledge that it contains very little readily recoverable ammonia.

That it was necessary to evaporate only 10% to of the spent regenerant solution, in order to obtain an ammonia solution having a higher concentration than that necessary for regeneration, was quite unexpected. also, a considerable increase in the amount of ammonia recovered when only about 1% to 1.5% of lime was added, comprised a step oi additional value. The addition of lime to the spent regenerant not only increased the amount of ammonia recovered by evaporating only a fraction of the spent regenerant liquid, but also prevented the formation of an objectionable cake in the condenser. When the cost of evaporating only a fraction oi the spent regenerant, and the addition of a relatively small percentage of lime, are compared with the savings in makeup ammonia, the economies effected are quite large, since lime is readily available and the spent regenerant liquid can be heated by waste steam, normally available in considerable quantities at a relatively low cost in a sugar factory. Thus, the operating costs tend to be quite low and the oost of the equipment, including the evaporator, condenser and piping, can usually be paid for Within a comparatively short period of time by the saving in ammonia which would otherwise need to be purchased.

It will be evident, of course, that changes may be made in the process of this invention. While lime, in the form of milk of lime or Ca(0{)2, is the preferred addition reagent, since it is readily available at sugar factories, other alkaline reagents may be used, such as sodium hydroxide or other alkaline hydroxides, added in equivalent proportions. As indicated, any particular portion of the discharge from the anion exchanger, as the result of regeneration and/or rinsing, may be varied considerably in point oi now, as between sending such discharge to the spent regenerant tank, to the ammonia makeup tank, to a rinse water supply tank, or to the sewer. Also, the particular percentage of spent regenerant to be evaporated may be Varied, usually in accordance with the concentration of ammonia necessary ior regeneration of a particular anion exchange material, as affected by the impurities removed, and other factors. In general, a suicient amount oi the ammonia is recovered from the spent regenerant to provide a substantial proportion of the ammonia necessary for regeneration of the next cell, such as The concentration of ammonia in the evaporated and condensed portion of the spent regenerant is preierably higher than the concentration necessary for regeneration, which in some instances may mean that a slightly smaller percentage of the spent regenerant will be evaporated, although the percentage of ammonia in the recovered regenerant may be smaller, to permit recovery of a greater proportion of the ammonia. By adding makeup ammonia, a considerably more concentrated solution can be produced at the makeup tank, so that variations in the percentage of ammonia in the liquid recovered from the spent regenerant may be compensated for when the makeup ammonia is added. Furthermore, it is also possible to pass a suicient amount of the rinse Water discharge to the ammonia makeup tank so that, with evaporated and condensed spent regenerant, the amount of liquid in the tank is suicient to fill the makeup tank, thus eiecting a saving in water, as when the latter is a sufficiently important factor. In the latter case, the ammonia concentration, if slightly low, may be increased by makeup ammonia.

It will be understood, of course, that other variations may occur, without departing from the spirit and scope of this invention.

What is claimed is:

1. In the treatment of sugar juice to remove impurities, wherein such juice is passed through a bed of cation exchange material and then through a bed of anion exchange material, such anion exchange material being capable of regeneration bv an ammonia solution having a concentration of between 2.5% and ammonia, and said anion exchange material being subjected to a water rinse after the passage of said ammonia solution therethrough, the improvement which comprises collecting at least a portion of the spent regenerant ammonia solution and at least a portion of such rinse water which contains ammonia, each after passage through said anion exchange material, to provide a spent regenerant solution having from about 0.15% to 1.7% concentration of ammonia; treating said spent solution with an alkaline hydroxide in proportion to not over 2% of calcium hydroxide; evaporating not over about 15% of said spent solution; and condensing said evaporant, so as to produce an aqueous ammonia solution having a concentration at least equal to between 2.5% and 5% for subsequent regeneration of anion exchange material.

2. In the treatment of sugar juice to remove impurities, as defined in claim 1, wherein said spent solution is treated with not over 1.5% of calcium hydroxide.

3. In the treatment of sugar juice to remove impurities, as defined in claim 1, wherein at least a portion of said water rinse of said anion exchange material comprises water previously passed through said cation exchange material for rinsing.

4. In the treatment of sugar juice to remove impurities, wherein such `juice is passed through a bed of cation exchange material and then through a bed of anion exchange material, such anion exchange material being'capable of regeneration by an ammo-nia solution having a concentration of between 21.5% and 5% ammonia, the combination of stepswhich comprise passing ammonia solution through said anion exchange material to regenerate the same; after the passage of said ammonia solution therethrough, passing rinse water through said anion exchange material, such rinse water tending to contain ammonia after such passage; collecting at least a portion of the spent regenerant ammonia solution and at least a portion of such rinse water containing ammonia, each after passage through said anion exchange material, to provide a spent regenerant solution having from about 0.15% to 1.7% concentration of ammonia; treating said spent solution with an alkaline hydroxidel in proportion toy not over 2% of calcium hydroxide; evaporating not over about 15% of said spent solution; and condensing said evaporant by heat exchange with additional spent solution being supplied for evaporation, so` as to produce an aqueous ammonia solution having a concentration at least equal to between 2.5% and 5% for subsequent regeneration of anion exchange material.

5. In the treatment of beet sugar juice to remove impurities, wherein such juice is passed through a bed of cation exchange material and then through a bed of anion exchange material, such anion exchange material being capable of regeneration by an ammonia solution having a concentration of between 2.5% and 5% ammo-nia and said anion exchange material is subjected to a water rinse after the passage of said ammonia solution therethrough, the improvement which comprises passing ammonia solution having an ammonia concentration of 2.5% to 5% from a makeup tank through said anion exchange material; collecting in a spent ammonia tank, the spent regenerant ammonia solution after passage through said anion exchange material; passing rinse Water from a rinse water tank through said anion exchange material; passing such rinse water, after passage through said anion exchange material, to said spent regenerant tank until the total solids therein begin to decrease and then to said makeup tank, said spent ammonia regenerant and ammonia bearing rinse water in said spent ammonia tank providing a spent regenerant solution having from about 0.15% to 1.7% concentration of ammonia; treating said spent solution with 1% to 1.5% of calcium hydroxide; evaporating between 10% and about 15% of said spent solution; condensf ing said evaporant by heat exchange with additional spent solution being supplied for evaporation, so as to produce a condensate aqueous ammonia solution having an ammonia concentration greater than 2.5%; passing said condensate to said makeup tank, said condensate and the portion of said rinse water passed to said makeup tank providing sufficient liquid for the regeneration of another bed of anion exchange material; and adding suiiicient makeup ammonia to produce an ammonia concentration in said makeup tank of 2.5% to 5%.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Mellor: Modern Inorganic Chemistry, revised ed., 1939, page 627. 

1. IN THE TREATMENT OF SUGAR JUICE TO REMOVE IMPURITIES, WHEREIN SUCH JUICE IS PASSED THROUGH A BED OF CATION EXCHANGE MATERIAL AND THEN THROUGH A BED OF ANION EXCHANGE MATERIAL, SUCH ANION EXCHANGE MATERIAL BEING CAPABLE OF REGENERATION BY AN AMMONIA SOLUTION HAVING A CONCENTRATION OF BETWEEN 2.5% AND 5% AMMONIA, AND SAID ANION EXCHANGE MATERIAL BEING SUBJECTED TO A WATER RINSE AFTER THE PASSAGE OF SAID AMMONIA SOLUTION THERETHROUGH, THE IMPROVEMENT WHICH COMPRISES COLLECTING AT LEAST A PORTION OF THE SPENT REGENERANT AMMONIA SOLUTION AND AT LEAST A PORTION OF SUCH RINSE WATER WHICH CONTAINS AMMONIA, EACH AFTER PASSAGE THROUGH SAID ANION EXCHANGE MATERIAL, TO PROVIDE A SPENT REGENERANT SOLUTION HAVING FROM ABOUT 0.15% TO 1.7% CONCENTRATION OF AMMONIA; TREATING SAID SPENT SOLUTION WITH AN ALKALINE HYDROXIDE IN PROPORTION TO NOT OVER 2% OF CALCIUM HYDROXIDE; EVAPORATING NOT OVER ABOUT 15% OF SAID SPENT SOLUTION; AND CONDENSING SAID EVAPORANT, SO AS TO PRODUCE AN AQUEOUS AMMONIA SOLUTION HAVING A CONCENTREATION AT LEAST EQUAL TO BETWEEN 2.5% AND 5% FOR SUBSEQUENT REGENERATION OF ANION EXCHANGE MATERIAL. 